The present invention relates to a sheet feeding device provided in a recording device of an electrophotographic copier, and more particularly relates to a manual sheet feeding device to feed transfer sheets made of various materials.
Transfer sheets used for image recording in an electrophotographic copier are usually accommodated in a sheet cassette detachably provided to the copier, and are then automatically fed.
The uppermost transfer sheet stacked on the sheet cassette is fed to an image forming section by the action of a semicircular roller and a separation claw in the prior art. The transfer sheets on the sheet cassette are fed one by one in the aforementioned manner.
In the case of manual feeding by which transparent sheets and thick sheets such as postcards are fed, the aforementioned separation claw can not be used, so that the following methods are used: a method by which transfer sheets are separated one by one by the action of a circular drive roller and a separation roller which comes into press contact with the circular drive roller and is connected with a torque limiter; and a method by which transfer sheets are separated one by one by the action of a circular drive roller and a friction pad which is brought into pressure contact with the circular drive roller.
However, in the case where the aforementioned methods are applied, the sheet separation device including the circular drive roller and the separation roller or the friction pad, pinches a transfer sheet even after a separating operation has been completed.
In order to release a transfer sheet from the transfer sheet separation device immediately after the completion of a separating operation, a semicircular roller of the prior art is well known. In this case, the semicircular roller is used as a separation roller together with a separation claw. The aforementioned technique is disclosed in Japanese Patent Application Open to Public Inspection No. 165837/1980.
According to Japanese Patent Application Open to Public Inspection No. 2146/1983, the object of the semicircular roller is to increase the conveyance force with respect to thin papers, and it can not be expected that the semicircular roller functions as a separation roller.
Accordingly, a strong conveyance force is required for a paper feeding roller for use in registration which is disposed downstream of the drive roller, so that a paper feeding roller of a simple registration system utilizing a shutter, can not be adopted, and accordingly the costs are increased.
Further, the following problem is caused. That is, when a transfer sheet is released from the drive roller after image formation has been started on the leading edge of the transfer sheet, the transfer sheet is jolted. As a result, slippage is caused in the transferred image.